Sterile test tubes

ABSTRACT

A test tube of plastic material having flattened-out, fused opposite ends and a chemically clean, completely sterile interior. In the preferred embodiment the end edges of the tube are rounded, both internally and externally. This minimizes retention of residual matter of the contents of the tube in the corners of the tube during practical use.

I United States Patent [1113,620,679

[72] Inventor Donald H. De Vaughn [56] References Cited 106 RidgewoodDrive, Sill Rafael, Calif. UNITED STATES PATENTS 94901 1,126,909 2/1915Stratton 215/32 UX 3; a fii g 1970 1,157,568 10/1915 Mills ...206/56 AAux P f t d 2,430,995 11/1947 RODS ...206/56 AA ux I a e o cation Se L 258" 3,036,894 5/1962 Forestiere 23/259 ux Pp P 3,068,154 12/1962 Majors23/259 ux 3 233 975 2/1966 McCormick 23/292 x dated Nov. 24, 1970.Divided and this application M an 16 1970 set. No. 3,322,266 5/1967Lontz et al 206/632 19,990 Primary Examiner-Joseph Scovronek AssistantExaminerD. G. Millman Attorney-Kurt A. Tauchen [54] STERILE TEST TUBES 3Claims 6 Drawing ABSTRACT: A test tube of plastic material havingflattened- [52] US. Cl. 23/259, out, fused opposite ends and achemically clean, completely 206/56 AA sterile interior. In thepreferred embodiment the end edges of [51] Int. CL B011 3/14 the tubeare rounded, both internally and externally. This [50] Field of Search23/292, minimizes retention of residual matter of the contents of thetube in the comers of the tube during practical use.

FATENTEDHUV 1 6 I971 INVENTOR.

DONALD H. DeVAUGHN STERILE TEST TUBES This is a division of my copendingU.S. Pat. application, Ser. No. 678,766 filed on Sept. 25, 1967, for aMethod Of Producing Sterile Test Tubes, now US. Pat. No. 3,542,618.

The present invention relates to test tubes, especially those used formedical purposes, such as blood tests, urine analyses, and the like.Such tubes should always be chemically clean and sterile at the time ofuse.

Object of the invention is to provide tubes whose interior is sterileand chemically clean and which remain clean and sterile without specialprecautions, such as sterile packaging, until they are prepared forpractical use.

Another object of the invention is to provide a test tube, of the typereferred to, that is easy to hold and handle during use and whose endsare of such conformation that. retention of residual matter during useis minimized.

These and other objects of the invention will be apparent from thefollowing description of the accompanying drawings which illustratecertain preferred embodiments thereof and wherein:

FIG. 1 is a schematic illustration of the first step in the method ofproducing the test tubes of my invention;

FIG. 2 is a schematic illustration, in the form of a flow line, of acomplete continuous process of producing the test tubes of my invention;

FIG. 3 is a schematic flow line similar to FIG. 2 illustrating aslightly modified embodiment of my invention;

FIG. 4 is a side elevation of a test tube in accordance with myinvention;

FIG. 5 is a plan view of the test tube shown in FIG. 4; and

FIG. 6 is a plan view of another type of test tube produced inaccordance with my invention.

In accordance with my invention I extrude tubing from plastic materialat a sterilizing temperature while injecting a gaseous substance, suchas nitrogen heated to a sterilizing temperature, at a superatmosphericpressure into the tubing as it is formed by and emerges from theextruder; and I subject the leading end of the newly formed tubing tocompression while it is still at a sterilizing temperature, to fuse itsflattened sidewalls and thus seal it hermetically. From then on as thetubing flows from the extruder and increases axially in length, Isubject it at a predetermined point of the production lineintermittently to compression under heat to fuse axially spaced sectionsof limited axial length of said tubing and thus convert it into asequence of tubular compartments having hermetically sealed ends; and Isever said compartments from each other at a subsequent point of theproduction line by suitable cutting means which are arranged to cutacross the fused tube sections without impairment of the hermetic sealsformed at the opposite ends of the compartments. The resultant tubesections have completely sterile and chemically clean interiors thatremain sterile and clean because their ends are hermetically sealed, andwhich may be shipped and stored and are ready for use without requiringany additional sterilization treatment or sterile packaging. All that isnecessary is to cut off one of their ends, or cut them into half, attheir place of use whereupon one or two chemically clean and completelysterile test tubes are immediately available.

In FIG. 1, the reference numeral 10 identifies an extruder ofconventional design. Powdered or pelleted plastic material such aspolypropylene, polyvinyl chloride or the polyethylene known under thetrade name Surlyn, is poured into the hopper of the extruder as shown at12, wherein it is heated to its melting point in the conventionalmanner, and from where it is extruded through the extrusion nozzle 14 inthe form of a tube 16 by rotation of the extrusion screw 18. Thepowdered or pelleted plastic raw material delivered into the extrudermust be chemically clean, and the softening points of all the exemplarymaterials mentioned hereinbefore lie above the minimum temperaturesrequired for sterilization. Thus, powdered polypropylene is heated to atemperature of 320 F. for the purpose of extrusion. As the extruder isoperated to expel a tube 19 of plastic material through its nozzle 14,heated nitrogen is continuously injected at a superatmospheric pressureinto the newly formed tubing 19, as schematically indicated by the line20 which passes through the extruder into the extrusion nozzle 14. Asthe gas in line 20 passes through the interior of the extruder, it issubjected to the heat applied to the extruder and heated to asterilizing temperature so that it cooperates with the heat of theextruded material to maintain the interior of the newly formed tubing 19sterile.

To penetrate into the newly formed tubing and to keep said tubing andthe sterile compartments subsequently formed from the tubing by themethod of my invention in inflated condition, the heated gas should beinjected into the newly formed tubing at a superatmospheric pressure,the exact mag nitude of which depends upon the nature of the plasticmaterial and the temperature employed to soften it. In the hereinbeforementioned practical embodiment of my invention wherein polypropylene wasused as raw material and a temperature of 320 F. was employed toestablish the required viscosity of the material, injection of theheated gas into the newly formed tubing at a pressure of about 2atmospheres was found satisfactory.

In accordance with the invention I subject the leading end 22 of thetubing emerging from the extrusion nozzle 14 to compression while it isstill at a sterilizing temperature, to flatten it out and to fuse itsflattened sidewalls together so that it forms a hermetical seal. Thus,it impossible for any micro-organisms to enter and contaminate theinterior of the tubing 19 from the outside, as it progresses from theextrusion nozzle 14 and cools below sterilizing temperatures. Thedescribed sealing process may be performed manually with a suitable pairof pliers or automatically by suitable placed sealing pads schematicallyindicated at 24 between which the emerging tubing is conducted and whichare briefly actuated but once at the beginning of the test tubeproduction method of my invention as shown in FIG. 1.

After the leading end 22 of the tubing 19 has been hermetically sealedin the described manner, it is passed through a cooling bath indicatedschematically at 25 in FIG. 2. This may be a trough containing runningwater at tap temperature. In the cooling bath the newly formed tubingacquires greater firmness and after leaving the bath it may now beengaged into a suitable mechanism for advancing it automatically, suchas between two endless belt conveyors 26a and 26b as indicated in FIG.2, whose belts are preferably made from rubber to grip the tubing andadvance it at the desired speed in the desired direction.

The conveyors 26a, 26b deliver the semihardened tubing to a stationwhereat axially spaced sections 30 of limited length of said tubing aresubjected to compression to flatten these sections and fuse theiropposite walls together. This can be done manually with suitable pliersor automatically by suitably placed heated pressure pads indicated at28a and 28b in FIG. 2. These pressure pads operate at predetermined timeintervals depending upon the speed of advance of the extruded tubing anddepending upon the desired length. of the tubes produced in accordancewith my invention. In this manner the tubing 19 produced by the extruder14 is converted into a sequence of separate tubular compartments 32 thatare hermetically sealed from each other by the fused sections 30, andwhose interior is completely sterile since entrance of livingmicro-organisms into the interior of the tubing 19 was prevented bypermanent closure of its leading end 22 while said end was still at asterilizing temperature.

It remains to separate the sealed tubular compartments thus formedwithout impairment of the hermetic seals at their opposite ends. Again,this may be done manually with scissors at a subsequent point of theproduction line established by the advancing tube, or it can be done byautomatic cutting mechanism symbolically indicated by the transversecutting blades 33a and 33b in FIG. 2 at a point which is preferablyremoved from the sealing station 28 by a distance equal to the desiredaxial length of the tube, or a suitable multiple of this distance. Saidcutting mechanism operates intermittently to cut transversely across thefused and flattened sections 30 of the tubing, whenever these sectionspass beneath the cutting knife.

An alternative arrangement is illustrated in FIG. 3 wherein the fusingof the tube sections and the separation of the tube compartments 32 intoindividual test tubes is done at one and the same station. This canagain be done manually or automatically by cutting pliers ofconventional design, i.e., pliers such as schematically indicated at 35in FIG. 3 of the type which can be operated to exert initially only asealing pressure upon the tube sections 30, and upon increased pressureproject a cutting blade or blades 36 to cut transversely through thecompressed tube sections after fusion has been accomplished. In otherwords, the arrangement schematically indicated at 35 in FIG. 3 may bemanually or automatically actuated to effect both the sealing of thedividing tube sections 30 and their separation in quick succession atthe same production station.

FIGS. 4 and illustrate the shape of a test tube 32 produced inaccordance with the invention. As best shown in FIG. 4, its ends 37 and38 are flattened out, and the opposite side areas produced by theflattening operation, are fused as shown at 40 to form hermetical seals.Test tubes with their ends thus flattened out are easy to hold and tohandle during practical use. While FIG. 5 shows the fused end portion 40of the tube as establishing straight or rectilinear edge lines 42,appropriate conformation of the compression pads and of the cuttingedges makes it possible to give these end edges a round or parabolicshape both, internally and externally, such as shown at 43 in FIG. 6,but care must be taken in the production of such rounded ends that theseal 40 established at the ends of the tubes by the flattened and fusedend portion thereof be not damaged. In test tubes with rounded andspecifically parabolic conformation of their end edges, there is alesser possibility that during use residual matter of its contents isretained in the tube.

' FIGS. 4 and 5 show the products of the invention to besingle-compartment tubular containers, which can be readily convertedinto one or two sterile test tubes at their place of use by cutting offone end thereof, or by cutting them into halves. By the processillustrated in FIG. 2 it is possible, however, to producemulticompartment containers, i.e. containers whose interior is dividedinto two or more compartments by a centrally located fused tube section45, with each compartment having a chemically clean and completelysterile interior, such as illustrated in FIG. 6. It is merely necessaryto synchronize the operation of the clamping mechanism 28 and thecutting mechanism 33 in such a manner that the latter will operate butonce for a predetermined multiple of phases of operation of the former.

The process of my invention makes it possible to produce chemicallyclean and interiorly completely sterile test tubes in large quantitiesin a simple and inexpensive manner, without special sterilizationtreatment; and the interior of these test tubes stays sterile up to themoment when they are used, without the necessity of providing forsterile packaging. The tubes are easy to hold and handle duringpractical use and the possibility that residual matter of their contentsbe retained in the comers of the tubes, is greatly minimized.

I claim:

1. A test tube of plastic material having a flattened-out, fused endportion wherein the internal contour of said end portion is of parabolicconformation.

2. A test tube of plastic material having flattened-out, fused oppositeends wherein the internal contour of said ends is parabolic in shape.

3. A test tube according to claim 2 including a flattened-out fusedsection intermediately of its opposite ends.

2. A test tube of plastic material having flattened-out, fused oppositeends wherein the internal contour of said ends is parabolic in shape. 3.A test tube according to claim 2 including a flattened-out fused sectionintermediately of its opposite ends.